Sarcomas primarily affect children and young adults. For pediatric oncologists, sarcomas are a major problem. Most are extremely aggressive and current protocols of surgery, radiation and chemotherapy are not adequate. Significant improvement for many sarcomas will require a detailed understanding of the genetic factors responsible for its progression, so that a gene targeted-based therapy can be developed to manage the cancer. Each sarcoma is likely to require its own specific molecular-based therapies for its management. To achieve these goals the information based for each sarcoma will likely require generating a mouse model of the human cancer that accurately simulates the human condition. The criterion to establish a good mouse model for the human cancer is now very rigorous. Each human cancer is being classified with a genetic fingerprint involving the expression profile of thousands of genes. Having established authenticity of the mouse model, it can be used to identify the secondary genetic events responsible for its progression. Having in turn identified the genetic players, their identity can be used as a platform to generate a rational approach to therapeutic development. We have successfully modeled alveolar rhabdomyosarcoma and synovial sarcoma and are in the process of modeling Ewing's sarcoma. We will use these mouse models to determine the secondary genetic events responsible for their progression. We also propose to generate improved third generation mouse models that will initiate the cancers by inducing the appropriate chromosomal translocation in their cell of origin. The therapeutic potential of iPS cells for cell-base therapy of many major human diseases is enormous. However, attaining this potential will require a much deeper understanding of adult stem cell biology, which is nature's normal means for maintaining tissue homeostasis and response to modest trauma. We propose to continue our functional studies of two adult stem cell systems, intestinal stem cells and neuronal stem cells. These two stem cell systems are at opposite ends of the spectrum in terms of the frequency of tissue turnover that they maintain. By comparing these two systems we may gain insights into how adult stem cell systems can be modulated to alter their output.